Bromus secalinus is a species of bromegrass known as rye brome.[2] The specific epithetsecalinus is Latin, meaning "rye-like". The fruits are hard, rounded glumes that appear superficially similar to the rye grain, which gives the brome its common and scientific name. The grass has a diploid number of 28.

The grass is native to Eurasia but is well known in many other parts of the world where it has been introduced. It is a noxious weed throughout much of North America.

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Bromus secalinus is an annual grass that grows 0.1–1.3 m (3.9 in–4 ft 3.2 in) high. The upper sheaths are smooth and strongly nerved, and the lower sheaths are glabrous or slightly pubescent. The leaf blades are 15–30 cm (5.9–11.8 in) long and 2–4 mm (0.079–0.157 in) wide, and are covered with short hairs. The panicles are 3–20 cm (1.2–7.9 in) long and 2.5–12 cm (0.98–4.72 in) wide with spreading or ascending branches. The spreading inflorescence nods when it becomes heavy with grain though prior to maturity the panicle is erect. The spikelets are on elongated pedicels, with each spikelet bearing five to fifteen flowers. The spikelets are glabrous or scabrous and become lax when mature. The ovoid spikelets measure 10–20 mm (0.39–0.79 in) long. The rachilla is obvious in youth and becomes obscured by the expanding florets with age. The lower glumes are three to five-veined and 4–6 mm (0.16–0.24 in) long, and the upper glumes are seven-veined and 6–7 mm (0.24–0.28 in) long. The lemmas become spreading when mature and are strongly inrolled. The lemmas have seven inconspicuous nerves and are 5–8 mm (0.20–0.31 in) long and 1.7–2.5 mm (0.067–0.098 in) wide. The awns are straight or curved and are 1–6 mm (0.039–0.236 in) long. The palea is as long or longer than the lemma and its tip slightly projects at maturity. The anthers are 1.5–1.8 mm (0.059–0.071 in) long. The caryopses are thick and strongly inrolled when mature.[3][4]

The grass flowers from June to September.

In youth the two brome grassesBromus secalinus and Bromus arvensis are very similar, but are easily distinguishable in maturity. Bromus arvensis has fully pubescent leaves but Bromus secalinus lacks trichomes on the undersides of leaves.[5]